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MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIFORNIA 91109. TELEPHONE (818) 354-5011
http://www.jpl.nasa.gov 

Alan Buis  (818) 354-0474
Jet Propulsion Laboratory, Pasadena, Calif.    

Lynn Chandler  (301) 286-2806
NASA Goddard Space Flight Center, Greenbelt, Md.                      
February 7, 2003

News Release: 2003-014

Space Sensors Sample Brews From Earth's Volcanic Cauldrons

Think of them as the Good Witches of the North, South, East and West,
whizzing around the globe daily on their techno "broomsticks" in
space.  When Europe's largest, most active volcano, Italy's Mount
Etna, cackled to life and spewed ash and noxious sulfur dioxide gases
last October, a quartet of remote sensing instruments from NASA's
Earth Observing System armada flew into action to analyze the smoky,
caustic potion.    

NASA's atmospheric science and volcanology wizards can now study the
evolution and structure of plumes from Mount Etna and Earth's 500 or
so other active volcanoes in greater detail than ever before.  They do
this by combining data from the Multi-angle Imaging SpectroRadiometer
(Misr), Moderate Resolution Imaging SpectroRadiometer (Modis) and the
joint U.S./Japan Advanced Spaceborne Thermal Emission and Reflection
Radiometer (Aster) sensors on NASA's Terra spacecraft with the
Atmospheric Infrared Sounder (Airs) and Modis sensors on NASA's Aqua
spacecraft.

"The synergies from NASA's remote sensing capabilities are helping us
understand the complex behavior of volcanic plumes and the effects
volcanic eruptions have on the environment," said Dr. Vince Realmuto,
a member of the Earth Observing System volcanology team and supervisor
of the Visualization and Scientific Animation Group at NASA's Jet
Propulsion Laboratory, Pasadena, Calif.  "By combining data from Airs,
Aster, Misr and Modis, we can study volcanic plumes and clouds from
many dimensions at once and observe targets of interest like Mount
Etna on a daily basis."  

Mount Etna's most recent eruption, which has subsided but not ended,
has released sulfur dioxide into the atmosphere at rates as high as
20,000 metric tons (44.1 million pounds) a day.  A major air pollutant
vented by some volcanoes, this gas rapidly converts to sulfate
aerosols in Earth's atmosphere, impacting local, regional and global
environments. 

"At the local and regional level, sulfate aerosols can affect air
quality and visibility and cause acid fog and rain, while their small
size allows them to penetrate deep into human lungs, impacting
respiratory health," Realmuto said.  "To affect global climate, these
aerosols have to make their way into Earth's upper atmosphere, or
stratosphere. 

"The eruptions of the Philippines' Mount Pinatubo in 1991 and Mexico's
El Chichon in 1982 deposited aerosols in the stratosphere and had
measurable effects on global climate," Realmuto continued.  "These
volcanic aerosol layers can reflect incoming solar radiation,
resulting in less radiation reaching the ground and throwing off the
radiation balance between the Earth, atmosphere and sun.  They can
trap greenhouse gasses, such as carbon dioxide and water vapor, rising
through the atmosphere.  They can also lead to the formation of polar
stratospheric clouds, a component of the process that destroys Earth's
protective ozone layer."

Airs, Aster and Modis all collect measurements in the thermal infrared
spectrum.  Sulfur dioxide, sulfate aerosols and volcanic ash are all
easily detectable in this spectral region.

The high spatial resolution of Aster makes it the only orbiting
instrument that can detect the non-explosive venting of sulfur dioxide
from small volcanic vents.  Aster's visible and near infrared channels
can also be used to determine some properties of aerosols and ash. 
Aster was built by Japan's Ministry of Economy, Trade and Industry and
has a joint U.S./Japan science team. 

Airs' high spectral resolution will allow scientists to identify the
components that make up volcanic plumes and estimate the quantity of
these components with greater accuracy.  In addition, Airs'
atmospheric temperature and relative humidity data will help
scientists develop thermal infrared models that can be used to
determine ash and aerosol makeup. 

Modis' spatial resolution falls in between that of Aster and Airs. 
Thus, Modis data are a bridge between the more localized Aster
measurements and the more regional Airs data.  Since Aster
observations of particular targets must be scheduled in advance, Modis
often provides the highest spatial resolution thermal infrared data
for a given eruption.  Both Modis and Airs transmit data in real
time-a key to monitoring volcanoes from space.

Misr's multi-angle imaging allows scientists to identify thin clouds
of airborne volcanic ash and aerosol plumes and estimate the abundance
and size of the particles.  For thicker plumes, Misr can determine the
height of the aerosol plume and the speed at which winds are moving
the plume through the atmosphere.  Knowing the plume height above the
ground is important to thermal infrared modeling because it determines
the temperature contrast between clouds and their backgrounds.  Wind
speed data are essential to accurately estimate the rate at which the
material is horizontally dispersed into the atmosphere.

NASA's Mount Etna images are at
 http://www.jpl.nasa.gov/releases/2003/14.cfm .
Misr information is at:
 http://www-misr.jpl.nasa.gov
Aster information is at
 http://asterweb.jpl.nasa.gov/.
Airs information is at
 http://www.jpl.nasa.gov/airs .
Modis information is at
 http://modis.gsfc.nasa.gov/ .

The California Institute of Technology in Pasadena manages JPL for 
NASA.  -end-

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